Pyrimidine derivatives and herbicidal method and compositions

ABSTRACT

A pyrimidine derivative having the formula: ##STR1## wherein R is hydrogen atom, --CH 2  CH 2  S(O) n  R 1  (wherein R 1  is a lower alkyl group, and n is an integer of from 0 to 2) or ##STR2## (wherein each R 1  is a lower alkyl group), A is a chlorine atom or a methoxy group, and each of D and E which may be the same or different, is a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group or a halogen-substituted lower alkoxy group, or a salt thereof.

The present invention relates to novel pyrimidine derivatives or theirsalts, processes for their production, herbicidal compositionscontaining them, and a herbicidal method for applying them.

U.S. Pat. Nos. 4,248,619 and 4,427,437 and Agr. Biol. Chem., Vol. 30,No. 9, p.896 (1966) disclose that 2-phenoxypyrimidine derivatives haveherbicidal activities.

However, the compounds disclosed in these references have a drawbackthat their herbicidal activities are inadequate.

The present inventors have conducted extensive research on pyrimidinederivatives with an aim to develop a compound having more excellentherbicidal activities, and as a result, have found that the compounds ofthe present invention having substituents introduced at specificpositions of the pyrimidine and benzene rings of phenoxypyrimidinederivatives, exhibit excellent herbicidal effects against perennialweeds as well as annual weeds, and at the same time, they have a highlevel of safety to crop plants, particularly to rice and wheat.

Namely, as compared with the compounds disclosed in U.S. Pat. No.4,248,619, the compounds of the present invention are superior in theherbicidal activities, particularly in the herbicidal activities in postemergence treatment. Further, the compounds of the present inventionhave a wide herbicidal spectrum, and they are capable of controlling ata relatively low dose weeds such as common cocklebur (Xanthiumstrumarium), morningglory (Ipomoea spp) and purple nutsedge (Cyperusrotundus) which are usually hardly controllable. Furthermore, thecompounds of the present invention have a high level of safety to ricein view of the low dose required for effectively controlling weeds.

The present invention has been accomplished on the basis of thesediscoveries.

The present invention provides a pyrimidine derivative having theformula: ##STR3## wherein R is a hydrogen atom, --CH₂ CH₂ S(O)_(n) R₁(wherein R₁ is a lower alkyl group, and n is an integer of from 0 to 2)or ##STR4## (wherein each R₁ is a lower alkyl group),A is a chlorineatom or a methoxy group, and each of D and E which may be the same ordifferent, is a hydrogen atom, a halogen atom, a lower alkyl group, alower alkoxy group or a halogen-substituted lower alkoxy group, or asalt thereof.

The present invention also provides a herbicidal composition comprisinga herbicidally effective amount of a pyrimidine derivative of theformula I or a salt thereof, and an agricultural adjuvant.

Further, the present invention provides a method for killing weeds whichcomprises applying a herbicidally effective amount of a pyrimidinederivative of the formula I or a salt thereof to a locus to beprotected.

The present invention also provides a process for producing a pyrimidinederivative of the formla I, which comprises reacting a2,6-dihydroxybenzoic acid ester having the formula: ##STR5## wherein Ris as defined above, with a 2-substituted 4,6-disubstituted pyrimidinehaving the formula: ##STR6## wherein A, D and E are as defined above,and X is a halogen atom, an alkylsulfonyl group or a benzylsulfonylgroup, in the presence of a base.

Further, the present invention provides a process for producing a2,6-bis[(4,6-disubstituted pyrimidin-2-yl)oxy]benzoic acid having theformula: ##STR7## wherein A, D and E are as defined above, whichcomprises subjecting a compound having the formula: ##STR8## wherein A,D and E are as defined above, and R₁ is a carboxyl-protecting groupselected from the group consisting of a lower alkylthioethyl group, amethoxybenzyl group and a trimethylsilylethyl group, to hydrolysis,hydrogenation or a reaction for removal of the carboxyl-protectinggroup.

Furthermore, the present invention provides a process for producing acompound having the formula: ##STR9## wherein A, D and E are as definedabove, and R₅ is --CH₂ CH₂ SR₁ (wherein R₁ is a lower alkyl group) or##STR10## (wherein each R₁ is a lower alkyl group), which comprisesesterifying a 2,6-bis[(4,6-disubstituted pyrimidin-2-yl)oxy]benzoic acidhaving the formula: ##STR11## wherein A, D and E are as defined above,with an alkylating agent or with an alcohol.

Now, the present invention will be described in detail with reference tothe preferred embodiments.

In the formula I, the lower alkyl group for each of R₁, D and E ispreferably a C₁ -C₄ alkyl group, the lower alkoxy group for each of Dand E is preferably a C₁ -C₄ alkoxy group, and the halogen-substitutedlower alkoxy group is preferably a halogen substituted C₁ -C₄ alkoxygroup.

Each of D and E which may be the same or different is preferably ahydrogen atom, a methoxy group or an ethoxy group, more preferably ahydrogen atom or a methoxy group. Particularly preferred is a compoundof the formula I wherein A is a methoxy group, and each of D and E is amethoxy group.

In the formula I, R is preferably hydrogen atom, --C₂ H₄ SCH₃, --C₂ H₄SC₂ H₅, --C₂ H₄ SOC₂ H₅ or --C₂ H₄ SO₂ C₂ H₅.

The salt of the pyrimidine derivative of the formula I may be an alkalimetal salt, an alkaline earth metal salt, a transition metal salt or anorganic ammonium salt. Particularly preferred is a triethanolamine salt,a diethanolamine salt, an ammonium salt, a sodium salt, a potassium saltor a calcium salt.

Now, typical examples of the compound of the present invention will bepresented in Table 1. Compound Nos. given in the Table will be referredto in the subsequent description in the specification.

                                      TABLE 1                                     __________________________________________________________________________     ##STR12##                                                                                                     Melting point                                                                 (°C.) of                                                               refractive                                   No.                                                                              R         A     D      E      index                                        __________________________________________________________________________    1  H         OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            148-150                                      2  C.sub.2 H.sub.4 SCH.sub.3                                                               OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            n.sub.D.sup.20 1.5706                        3  C.sub.2 H.sub.4 SC.sub.2 H.sub.5                                                        OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            76-79                                        4  C.sub.2 H.sub.4 SOC.sub.2 H.sub.5                                                       OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            89-90                                        5  C.sub.2 H.sub.4 SO.sub.2 C.sub.2 H.sub.5                                                OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            92-96                                        6  H         OCH.sub.3                                                                           Cl     OCH.sub.3                                                                            150-152                                      7  H         OCH.sub.3                                                                           CH.sub.3                                                                             CH.sub.3                                                                             174-177                                      8  H         OCH.sub.3                                                                           H      H      120-125                                      9  H         OCH.sub.3                                                                           Cl     CH.sub.3                                                                             133-136                                      10 H         OCH.sub.3                                                                           CH.sub.3                                                                             OCH.sub.3                                                                            150-152                                      11 H         OCH.sub.3                                                                           H      OCH.sub.3                                                                            132-135                                      12 H         Cl    Cl     OCH.sub.3                                                                            149-150                                      13 H         OCH.sub.3                                                                           H      CH.sub.3                                                                             153-157                                      14 H         OCH.sub.3                                                                           OC.sub.2 H.sub.5                                                                     OC.sub.2 H.sub.5                                                                     143-144                                      15 H         OCH.sub.3                                                                           OCHF.sub.2                                                                           OCHF.sub.2                                                                           127-130                                      16 H         OCH.sub.3                                                                           H      Cl     83-88                                        17 •NH.sub.3 C.sub.3 H.sub.7i                                                        OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                             99-102                                      18 •Na OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            235-237                                      19 •HN(C.sub.2 H.sub.4 OH).sub.3                                                     OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            103-110                                      20 •H.sub.2 N(C.sub.2 H.sub.4 OH).sub.2                                              OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            n.sub.D.sup.20 = 1.5528                      21                                                                                ##STR13##                    89-95                                        22 •NH.sub.4                                                                         OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            135-140                                      23                                                                                ##STR14##                                                                              OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            114-117                                      24                                                                                ##STR15##                                                                              OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            121-122                                      25                                                                                ##STR16##                                                                              OCH.sub.3                                                                           OCH.sub.3                                                                            OCH.sub.3                                                                            112-114                                      26                                                                                ##STR17##                                                                              OCH.sub.3                                                                           H      H      n.sub.D.sup.20 = 1.5571                      __________________________________________________________________________

Among the compounds of the present invention, benzoic acid derivativeswherein R is a hydrogen atom, or their salts exhibit particularlyexcellent herbicidal effects.

Compound Nos. 1, 17, 18, 19, 20, 21 and 22 are particularly superior inthat they have excellent herbicidal activities and no substantialphytotoxicity against crop plants, particularly rice and wheat.

The compounds of the present invention can be prepared in accordancewith the following processes. ##STR18##

In the above formulas, R₁ is a lower alkyl group, R₂ is a hydrogen atom,a lower alkylthioethyl group, a benzyl group or a methoxybenzyl group,R₃ is a benzyl group or a methoxybenzyl group, R₄ is a benzyl group,methoxybenzyl group, or a trimethylsilyl group, R₅ is ##STR19## (whereinR₁ is as defined above) or --CH₂ CH₂ SR₁ (wherein R₁ is as definedabove), X is a halogen atom, an alkylsulfonyl group or a benzylsulfonylgroup, A, D and E are as defined above, and m is 1 or 2.

The 2,6-dihydroxybenzoic acid ester of the formula II can be prepared byreacting 2,6-dihydroxybenzoic acid with a halogenated alkane in thepresence of a base preferably in a solvent, or by reacting an alcoholwith a condensing agent such as carbonyl diimidazole preferably in asolvent.

PROCESS A:

The compound of the formula VI can be prepared by reacting the compoundof the formula II with the compound of the formula III in the presenceof at least 2 equivalent of a base in a solvent at a temperature withina range of from room temperature to the boiling point of the solvent forfrom 0.5 to 48 hours. As the base, an alkali metal such as sodium metal,potassium metal, an alkali metal hydride or alkaline earth metalhydride, such as potassium hydride or calcium hydride, an alkali metalcarbonate such as sodium carbonate or potassium carbonate, or an organicamine such as triethylamine or pyridine, may be employed.

As the solvent, a hydrocarbon solvent such as benzene, toluene orxylene, a halogenated hydrocarbon solvent such as methylene chloride orchloroform, an alcohol solvent such as methanol, ethanol or 2-propanol,an ether solvent such as diisopropyl ether, tetrahydrofuran or dioxane,a ketone solvent such as acetone or methyl ethyl ketone, an estersolvent such as methyl acetate or ethyl acetate, an aprotic polarsolvent such as dimethylformamide, dimethylacetamide ordimethylsulfoxide, acetonitrile, water or a mixture thereof, may beused.

The molar ratios of the compound of the formula II and the compound ofthe formula III are preferably one equivalent of the former and twoequivalent of the latter. However, the compound of the formula VI can beprepared even when the compound of the formula II or the compound of theformula III is excessive within a range of from 1.1 to 1.2 times.

PROCESS B:

A compound of the formula I wherein R is a hydrogen atom can be preparedby the reaction in accordance with Process A using at least threeequivalent of a base, followed by acidification.

Further, it can also be prepared from a compound of the formula V bycatalytic reduction with hydrogen.

PROCESS C:

A compound of the formula I wherein R is --CH₂ CH₂ S(O)_(m) R₁ whereinR₁ is as defined above, and m is an integer of 1 or 2, can be preparedby oxidizing the compound of the formula VII in a solvent by means of anoxidizing agent.

PROCESS D:

Then, a compound of the formula IX can be prepared by reacting oneequivalent of the compound of the formula II and one equivalent of thecompound of the formula III. Then, after isolating it or withoutisolating it, a compound of the formula X can be prepared. From thecompound of the formula X, a compound of the formula XI can be preparedin accordance with Process B.

PROCESS E:

A compound of the formula XIV is prepared from the compounds of theformulas XII and XIII in accordance with Process A or D. When R₄ is atrimethylsilylethyl group, it is reacted with tetrabutylammoniumfluoridetrihydrate to obtain a compound of the formula I.

PROCESS F:

The compound of the formula VI is imidazolyl-modified or halogenatedwith carbonyl diimidazole, thionyl chloride, oxalic acid chloride orphosgene, followed by a reaction with dialkylketone oxime to obtain acompound of the formula XV.

2,6-bis[(4,6-dimethoxypyrimidine-2-yl)oxy]benzoic acid thus prepared,can be converted to its alkali metal salt by reacting it with an equalamount of sodium bicarbonate, sodium hydroxide, potassium hydroxide orsodium hydride.

Then, the alkali metal salt may be reacted with calcium chloride, or thecorresponding benzoic acid is reacted with calcium carbonate or calciumhydride, to obtain an alkaline earth metal salt. Further, the alkalimetal salt may be reacted with iron chloride to obtain a transitionmetal salt such as an iron salt.

Further, it is possible to convert the benzoic acid to an organicammonium salt by reacting it with an aliphatic amine such as a primaryamine, a secondary amine, a tertiary amine, diethanol amine, triethanolamine, an alkoxyalkylamine, a cyclohexylamine or morphorine, or with anaromatic amine such as aniline or naphthylamine.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

EXAMPLE 1 Preparation of isopropylammonium 2,6-bis[(4,6-yl)oxy]benzoicacid (Compound No. 1)

2.0 g (3.8 mmol) of benzyl2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate (melting point:130°-132° C.) was dissolved in methanol. The solution was added to 0.3 gof 10% palladium-carbon preliminarily wetted with acetic acid andmethanol. Hydrogen was introduced under atmospheric pressure to conductcatalytic reduction. When absorption of hydrogen ceased, the reactionwas regarded as terminated, and the reaction solution was subjected tofiltration. The filtrate was concentrated under reduced pressure. Then,to the residue, ethyl acetate and water were added for liquidseparation. The ethyl acetate layer was washed with water, dried andconcentrated. Crystals thereby obtained were washed with hexane toobtain 1.0 g of a white powder having a melting point of from 148° to150° C.

EXAMPLE 2 Preparation of2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid Compound No. 1)

By using 5.5 g (10 mmol) of 4-methoxybenzyl2,6-bis[(4,6-dimethoxypyridin-2-yl)oxy]benzoate (melting point: 82°-83°C.), the operation was conducted in the same manner as in Example 1 toobtain 3.0 g of the desired compound as a white powder having a meltingpoint of from 148° to 150° C.

EXAMPLE 3 Preparation of 2-ethylsulphenylethyl2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate (Compound No. 4)

24.0 g (46.3 mmol) of 2-ethylthioethyl2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate was dissolved inchloroform. Then, a chloroform solution prepared by dissolving 8.8 g ofm-chloroperbenzoate under cooling with ice, was dropwise added theretoat a temperature of from 5° to 10° C. The mixture was reacted at thesame temperature for one hour. Then, an aqueous sodium sulfite solutionwas added thereto, and the mixture was subjected to liquid separation.The organic layer was washed with an aqueous sodium bicarbonatesolution, dried and concentrated to obtain 23.5 g of a slightly brownviscous substance. This substance was solidified, and the solid showed amelting point of from 88° to 90° C.

EXAMPLE 4 Preparation of2-(4-chloro-6-methoxypyrimidin-2-yl)oxy-6-(4,6-dimethoxypyrimidin-2-yl)oxybenzoicacid (Compound No. 6)

(1) Preparation of trimethylsilylethyl2-(4-chloro-6-methoxypyrimidin-2-yl)oxy-6-(4,6-dimethoxypyrimidin-2yl)oxybenzoate

NaH (0.4 g, purity: 60%) was suspended in 50 ml of THF. To thissuspension, trimethylsilylethyl6-(4,6-dimethoxypyrimidin-2-yl)oxysalicylate (3.0 g) was added, and themixture was stirred at room temperature for 30 minutes. To this mixture,4-chloro-6-methoxy-2-methylsulfonylpyrimidine (1.8 g) was added, and themixture was stirred at room temperature for further 12 hours. Aftercompletion of the reaction, water was added thereto, and the mixture wasextracted with ethyl ether. The ethyl ether layer was dried overanhydrous magnesium sulfate. Then, the solvent was distilled off underreduced pressure. The crude extract thus obtained was purified by silicagel column chromatography to obtain the above identified compound as aslightly yellow liquid (4.0 g).

(2) Preparation of2-(4-chloro-6-methoxypyrimidin-2-yl)oxy-6-(4,6-dimethoxypyrimidin-2-yl)oxybenzoicacid

Trimethylsilylethyl2-(4-chloro-6-methoxypyrimidin-2-yl)oxy-6-(4,6-dimethoxypyrimidin-2-yl)oxybenzoate(4.0 g) was dissolved in 30 ml of DMF. To this solution,tetrabutylammonium fluoride trihydrate (5.9 g) was added, and themixture was stirred at room temperature for 15 minutes. After completionof the reaction, water and a small amount of an aqueous potassiumhydrogen sulfate solution were added thereto, and the mixture wasextracted with ethyl acetate. The organic layer was washed with asaturated sodium chloride aqueous solution and then dried over anhydrousmagnesium sulfate. The solvent was distilled off under reduced pressure,and the crystals thereby obtained were washed with a mixture of hexaneand IPE to obtain the above identified compound as white crystals (3.2g). (Melting point: 150°-152° C.)

EXAMPLE 5 Preparation of isopropylammonium2,6-bis[(4,6-dimethoxypyrimidin-2-yl)Oxy]benzoate (Compound No. 17)

2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (2.0 g) andisopropylamine (1.0 9) were dissolved in 30 ml of THF, and the mixturewas stirred at room temperature for 12 hours. The reaction solution wasconcentrated, and crystals thereby precipitated, were washed with hexaneto obtain the above identified compound as white crystals (1.9 g).(Melting point: 99°-102° C.)

EXAMPLE 6 Preparation of isopropylidene aminoester of2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (Compound No. 23)

2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (3.0 g) andN,N'-carbonyldiimidazole (1.2 g) were dissolved in 50 ml of THF, and thesolution was refluxed under heating for 15 minutes. To this reactionsolution, acetone oxime (0.6 g) was added, and the mixture was refluxedunder heating for further 16 hours.

After completion of the reaction, water was added thereto, and themixture was extracted with ethyl acetate. The organic layer was washedwith a saturated sodium chloride aqueous solution and dried overanhydrous magnesium sulfate. Then, the solvent was distilled off underreduced pressure. The crude extract thus obtained was purified by silicagel column chromatography to obtain the above identified compound aswhite crystals (2.1 g). (Melting point: 114°-117° C.)

EXAMPLE 7 Preparation of tris(2 hydroxyethyl)ammonium2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate (Compound No. 19)

2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (2.0 g) andtriethanolamine (0.7 g) were dissolved in 30 ml of THF, and the solutionwas stirred at room temperature for 12 hours.

The reaction solution was concentrated, and crystals therebyprecipitated were washed with hexane to obtain the above identifiedcompound as white crystals (2.4 g). (Melting point: 103°-110° C.)

EXAMPLE 8 Ammonium 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate(Compound No. 22)

2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (5.1 g) and 28%aqueous ammonia (1.7 g) were mixed with a solvent mixture ofTHF/ethanol. Precipitated crystals were washed with acetone to obtainthe above identified compound as white crystals (3.7 g). (Melting point:135°-140° C.

EXAMPLE 9 Preparation of methylthioethyl2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate (Compound No. 2)

Methylthioethyl 2,6-dihydroxybenzoate (4.5 g) was dissolved in DMF, and60% sodium hydride (1.6 g) was added thereto. Then, 2chloro-4,6-dimethoxypyrimidine (3.5 g) was added thereto, and themixture was heated and reacted at a temperature within a range of from90° to 10° C. for two hours. The reaction solution was poured into icewater and then extracted twice with ethyl acetate. The ethyl acetatelayer was washed with water and dried over anhydrous sodium sulfate.After removing inorganic substances by filtration, the solvent wasdistilled off under reduced pressure. The residue was purified by columnchromatography to obtain the above identified compound as a colorlessviscous liquid. (η_(D) ²⁰ : 1.5706).

EXAMPLE 10 Preparation of2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid (Compound No. 1)

60% sodium hydride (1.4 g) was suspended in THF. To the suspension,benzyl 2,6-dihydroxybenzoate (8.0 g) was added, and the mixture wasstirred at room temperature for 15 minutes. Then,4,6-dimethoxy-2-methylsulfonyl pyrimidine (7.8 g) was added thereto, andthe mixture was reacted for 8 hours under reflux.

After cooling, the reaction solution was poured into water and extractedwith ethyl ether. The organic layer was washed with a saturated sodiumchloride aqueous solution and dried over anhydrous magnesium sulfate.The solvent was distilled off under reduced pressure. The residue waspurified by silica gel column chromatography to obtain benzyl6-(4,6-dimethoxypyrimidin-2-yl)oxysalicylate (2.0 g) as white crystals.(Melting point: 63°-65° C.)

Benzyl 6-(4,6-dimethoxypyrimidin-2-yl)oxysalicylate thus obtained, wasreacted with 4,6-dimethoxy-2-methylsulfonylpyrimidine in the same manneras in Example 4 to obtain benzyl2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate (Melting point:130°-132° C. as white needle-like crystals).

Benzyl 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate thus obtained,was hydrolyzed in the same manner as in Example 1 to obtain2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic aicd as a white powder.(Melting point: 148°-150° C.)

EXAMPLE 11 Preparation of2,6-bis{[(4-chloro-6-methoxy)pyrimidin-2-yl]oxy}benzoic acid (CompoundNo. 12)

60% sodium hydride (1.6 g) was suspended in THF. To the suspension,2,6-dihydroxybenzoic acid (2.0 g) was added, and the mixture was stirredat room temperature for 30 minutes. Then,4-chloro-6-methoxy-2-methylsulfonylpyrimidine (5.8 g) was added thereto,and the mixture was reacted at room temperature for two days.

After the reaction, the reaction solution was poured into water andextracted with ethyl acetate. The organic layer was washed with asaturated sodium chloride aqueous solution and dried over anhydroussodium sulfate. The solvent was distilled off under reduced pressure.The residue was purified by column chromatography to obtain the aboveidentified compound (1.6 g) as slightly yellow crystals. (Melting point:149°-150° C.)

The herbicidal composition of the present invention comprises aherbicidally effective amount of the compound of the present inventionand an agricultural adjuvant. The herbicide of the present invention maybe used as it is or may be formulated in various formulations such as awettable powder, a granule, an emulsifiable concentrate or a dust byblending it in an amount of from 0.5 to 95 parts by weight, preferablyfrom 1 to 80 parts by weight, with a carrier, a surfactant, a dispersingagent or an adjuvant which is commonly employed for the formulation ofagricultural chemicals, in an amount to make up the total of 100 partsby weight.

As the carrier to be used for the formulation, there may be mentioned asolid carrier such as jeeklite, talc, bentonite, clay, kaolin,diatomaceous earth, white carbon, vermiculite, slaked lime, silica sand,ammonium sulfate or urea, or a liquid carrier such as isopropyl alcohol,xylene, cyclohexane or methyl naphthalene. As the surfactant anddispersing agent, there may be mentioned, for example, analcohol-sulfuric acid ester, an alkyl aryl sulfonate, lignin sulfonate,a polyoxyethylene glycol ether, a polyoxyethylene alkyl aryl ether or apolyoxyethylene sorbitol mono-alkylate. As the adjuvant, for example,carboxymethyl cellulose, polyethylene glycol or gum arabic may bementioned.

The proportion of the compound of the present invention in theformulation may vary depending upon the type of the formulation, theapplication method, the application site, timing, etc. Therefore, it cannot generally be defined. However, it is usually from 5 to 0% by weightin a wettable powder, from 5 to 80% by weight in an emulsifiableconcentrate, from 1 to 60% by weight in a flowable, from 0.5 to 20% byweight in a granule, from 5 to 40% by weight in a liquid formulation,from 0.5 to 10% by weight in a dust and from 5 to 90% by weight in a dryflowable.

A liquid formulation can be prepared either by using the activeingredient in the form of a salt, or by adding a basic substance to theactive ingredient in the form of an acid at the time of formulation. Inpractical use, such a herbicide may be diluted to a suitableconcentration before application, or may directly be applied.

The herbicide of the present invention is capable of controlling variousweeds in an agricultural field such as an upland field or an orchard, orin a forest, a lawn or other non-agricultural field by soil treatmentbefore or after the emergence of weeds or by foliage treatment. Further,the herbicide is capable of controlling various weeds in a paddy fieldby irrigated soil treatment before or after the emergence of weeds or byfoliage treatment.

For soil treatment, the herbicide of the present invention is applied ina dose of from 0.1 g to 1 kg, preferably from 0.5 to 500 g, morepreferably from 1 to 100 g, of the active ingredient per 10 ares. Forfoliage treatment, it is diluted to a concentration of from 1 to 0,000ppm for application. Most preferably, it is applied in a dose of from 1to 10 g of the active ingredient per 10 ares for a paddy field, in adose of from 5 to 50 g per 10 ares for an orchard or a lawn, and in adose of from 10 to 100 g for a forest or a nonagricultured field.

Now, Formulation Examples for the herbicidal composition of the presentinvention will be given. However, it should be understood that thepresent invention is by no means restricted to these specific Examples.In these Examples, "%" means "% by weight".

FORMULATION EXAMPLE 1 (wettable powder)

10% of Compound No. 1, 0.5% of Emulgen 810 (trademark, Kao Corporation),0.5% of Demol N (trademark, Kao Corporation), 20% of Kunilite 201(trademark, Kunimine Kogyo K.K.) and 69% of Jeeklite CA (trademark,Jeeklite Company Ltd.) were uniformly mixed and pulverized to obtain awettable powder.

FORMULATION (emulsifiable concentrate)

30% of Compound No. 1, 20% of cyclohexanone, 11% of polyoxyethylenealkyl aryl ether, 4% of calcium alkylbenzenesulfonate and 35% of methylnaphthalene, were uniformly dissolved to obtain an emulsifiableconcentrate.

FORMULATION EXAMPLE 3 (granule)

5% of Compound No. 1, 2% of a sodium salt of a lauryl alcohol-sulfuricacid ester, 5% of sodium lignin sulfonate, 2% of carboxymethyl celluloseand 86% of clay were uniformly mixed and pulverized. To 100 parts byweight of this mixture, 20 parts by weight of water was added, and themixture was kneaded, and granulated into granules of from 14 to 32 meshby means of an extrusion granulating machine, followed by drying toobtain granules.

FORMULATION EXAMPLE 4 (dust)

2% of Compound No. 2, 5% of diatomaceous earth and 93% of clay wereuniformly mixed and pulverized to obtain a dust.

The compounds and the herbicidal compositions of the present inventionare capable of effectively controlling annual weeds such as barnyardgrass (Echinochloa crusgalli), crabgrass (Digitaria sanquinalis),goosegrass (Eleusine indica), green foxtail (Setaria viridis), waterfoxtail (Alopecurus aequalis), annual bluegrass (Poa annua), wild oat(Avena fatua), italian ryegrass (Lolium multiflorum), smartweed(Polygonum lapathifolium), slender amaranth (Amaranthus viridis),lambsquarters (Chenopodium album), velvetleaf (Abutilon theophrasti),prickly sida (Sida sponosa), siclepod (Cassia tora), chichweed(Stellaria media), morning glory (Ipomea spp), common cocklebur(Xanthium strumarium), rice flatsedge (Cyperus iria), broadleafsignalgrass (Brachiaria platyphylla), itchgrass (Rottoboelia exaltata),downy brome (Bromus tectorum), wild buckwheat (Polygonum convolvulus),wild mustard (Brassica arvensis) and devils beggarticks (Bidensfrondosa), and perennial weeds such as purple nutsedge (Cyperusrotudus), johnosongrass (Sorghum halepense), bermudagrass (Cynodondactylon) and quackgrass (Agropyron repens) grown in upland fieldsincluding agricultural fields, orchards and nonagricultural fields.

Further, they are capable of effectively controlling annual weeds suchas barnyardgrass (Echinochloa crusgalli), flatsedge (Cyperus difformis),monochoria (Monochoria vaginalis), and perennial weeds such as bulrush(Scirpus hotarui) Alisma canaliculatum, Cyperus serotinus, Sagittariapygmaea and Eleocharis kuroguwai, grown in paddy fields. Furthermore, asherbicides for lawns, they are capable of controlling annual weeds suchas crabgrass (Digitaria sanguimalis), annual bluegrass (Poa annua) andcreeping woodsorrel (Oxalis corniculata), and perennial weeds such aspurple nutsedge (Cyperus rotundas) grown in golf fields or gardens. Theyare also capable of controlling perennial weeds such as kudzu (Puerariathunbergiana), Japanese plume grass (Miscanthus sinensis Anderss) andbamboo grass (Pleiblastus spp.) grown in forests.

Now, the herbicidal activities of the herbicides of the presentinvention will be described with reference to Test Examples.

The compounds of the present invention have the following features:

(1) They have high herbicidal effects, and they are very effective at alow dose.

(2) They are highly effective in soil treatment before emergence.However, they are particularly effective in foliage treatment afteremergence.

(3) They have a wide herbicidal spectrum. (They are effective not onlyagainst annual weeds belonging to rice, broadleaf or cyperaceous weedfamily, but also perennial weeds belonging to rice, broadleaf orcyperaceous weed family.

(4) They have a high level of safety to crop plants. Particularly, theyare highly safe to rice, wheat and lawn. They can safely be used alsofor transplanted paddy field rice.

(5) They are herbicidally highly effective even against weeds of ahighly advanced leafstage (i.e. highly grown weeds).

(6) They do not remain in soil and give no adverse effects to rotatedcrops.

(7) They have no substantial toxicity against mammal or fish and have ahigh level of safety thereto.

Now, the herbicidal activities of the herbicides of the presentinvention will be described with reference to Test Examples.

The following abbreviations represent the following test plants:

Or: rice, Tr: wheat, EC: barnyardgrass,

Se: green foxtail, Po: smartweed, Am: slender amaranth, Ip:morningglory, Xa: common cocklebur,

Cr: purple nutsedge, Di: crabgrass,

Ch: lambsquarters, Ci: rice flatsedge, Cd: flatsedge,

Mo: monochoria, Sc: bulrush, So: Johnsongrass,

Al: water foxtail and Ab: velvetleaf

TEST EXAMPLE 1 (foliage tretment in upland field)

In a pot filled with soil (surface area: 100 cm2), seeds ofbarnyardgrass (Ec), crabgrass (Di), smartweed (Po), slender amaranth(Am), lambsquarters (Ch) and rice flatsedge (Ci), were sown and coveredwith soil in a thickness of from 0.5 to 1 cm. The pot was cultured in agreen house at a temperature of from 20° to 25° C. for 2 weeks, and thena predetermined amount of a wettable powder prepared in accordance withFormulation Example 1 was diluted with water, and applied to the foliageat a rate of 100 liters per 10 ares (dose of active ingredient: 400 g/10ares). The evaluation was conducted on the 14th day after the treatmentin accordance with the standard as identified in Table 2. The resultsare shown by the index numbers in Table 3.

                  TABLE 2                                                         ______________________________________                                        Index No.   Herbicidal effects and Phytotoxicity                              ______________________________________                                        0           No herbicidal effect (or no phytotoxicity)                        1           Herbicidal effect (or phytotoxicity): more                                    than 0% and less than 30%                                         2           Herbicidal effect (or phytotoxicity): at                                      least 30% and less than 50%                                       3           Herbicidal effect (or phytotoxicity): at                                      least 50% and less than 70%                                       4           Herbicidal effect (or phytotoxicity): at                                      least 70% and less than 90%                                       5           Herbicidal effect (or phytotoxicity): more                                    than 90%                                                          ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Compound    Herbicidal effects                                                No.         Ec    Di      Po  Am     Ch  Ci                                   ______________________________________                                        1           5     5       5   5      5   5                                    2           5     5       5   5      5   5                                    3           4     4       4   5      5   2                                    4           5     5       5   5      4   4                                    5           5     5       5   5      4   4                                    6           5     5       4   5      5   5                                    8           5     5       5   5      5   5                                    11          5     4       5   5      5   5                                    14          5     5       5   5      4   5                                    16          5     4       5   5      5   5                                    17          5     5       5   5      5   5                                    18          5     5       5   5      5   5                                    19          5     5       5   5      5   5                                    20          5     5       5   5      5   5                                    21          5     5       5   5      5   5                                    22          5     5       5   5      5   5                                    23          5     5       5   5      5   5                                    24          5     5       5   5      5   5                                    25          5     5       5   5      5   5                                    26          5     5       5   5      4   5                                    ______________________________________                                    

TEST EXAMPLE 2 (soil treatment in upland field)

In a pot filled with soil (surface area: 100 cm²), seeds ofbarnyardgrass (Ec), crabgrass (Di), smartweed (Po), slender amaranth(Am), lambsquarters (Ch) and rice flatsedge (Ci) were sown and coveredwith soil in a thickness of from 0.5 to 1 cm. One day later from theseeding, a predetermined amount of a wettable powder prepared inaccordance with Formulation Example 1, was diluted with water andapplied to the soil surface at a rate of 100 liters per 10 ares (dose ofactive ingredient: 400 g/10 ares). The evaluation was conducted on the20th day after the treatment in accordance with the standard asidentified in Table 2. The results are shown by the index numbers inTable 4.

                  TABLE 4                                                         ______________________________________                                        Compound    Herbicidal effects                                                No.         Ec    Di      Po  Am     Ch  Ci                                   ______________________________________                                        1           5     5       5   5      5   5                                    6           5     5       5   5      5   5                                    7           5     5       5   5      5   5                                    8           5     5       5   5      5   5                                    10          5     4       5   5      5   5                                    11          5     5       5   5      5   5                                    12          5     4       5   5      5   5                                    13          5     5       5   5      5   5                                    14          4     5       5   5      5   5                                    15          5     5       5   5      5   5                                    17          5     5       5   5      5   5                                    18          5     5       5   5      5   5                                    19          5     5       5   5      5   5                                    20          5     5       5   5      5   5                                    21          5     5       5   5      5   5                                    22          5     5       5   5      5   5                                    23          5     5       5   5      5   5                                    24          5     5       5   5      5   5                                    25          5     5       5   5      5   5                                    ______________________________________                                    

TEST EXAMPLE 3 (test of controlling weeds in paddy field)

In a pot filled with paddy field soil (surface area: 100 cm²), seeds ofbarnyardgrass (Ec), flatsedge (Cd), monochoria (Mo) and bulrush (Sc)were sown, and water was introduced to a depth of 3 cm. Two days laterfrom the seeding, a predetermined amount of wettable powder prepared inaccordance with Formulation Example 1, was diluted with water anddropwise applied to the water surface in a dose of 100 g of the activeingredient per 10 ares. The evaluation was conducted on the 21st dayafter the treatment in accordance with the standard as identified inTable 2. The results are shown by the index numbers in Table 5.

                  TABLE 5                                                         ______________________________________                                        Compound     Herbicidal effects                                               No.          Ec    Cd          Mo   Sc                                        ______________________________________                                        1            5     5           5    5                                         2            5     5           5    5                                         3            4     5           5    5                                         4            4     5           5    4                                         5            5     5           5    5                                         6            5     5           5    5                                         7            5     5           5    5                                         8            5     5           5    5                                         9            5     5           5    5                                         10           5     5           5    5                                         11           5     5           5    5                                         12           5     5           5    5                                         13           5     5           5    5                                         14           5     5           5    5                                         15           5     5           5    5                                         16           5     5           5    5                                         17           5     5           5    5                                         18           5     5           5    5                                         19           5     5           5    5                                         20           5     5           5    5                                         21           5     5           5    5                                         22           5     5           5    5                                         23           5     5           5    5                                         24           5     5           5    5                                         25           5     5           5    5                                         ______________________________________                                    

TEST EXAMPLE 4 (selective herbicidal test)

In a pot filled with soil (surface area: 600 cm²), seeds of rice (Or),wheat (Tr), barnyardgrass (Ec), green foxtail (Se), smartweed (Po),slender amaranth (Am), morningglory (Ip) and common cocklebur (Xa) weresown, tubers of purple nutsedge (Cr) were planted and covered with soilin a thickness of from 0.5 to 1 cm. The pot was cultured in a greenhouse at a temperature of from 20 to 25° C. for 2 weeks, and then, apredetermined amount of a wettable powder prepared in accordance withFormulation Example 1 was diluted with water, and applied to the foliageat a rate of 100 liters per 10 ares. The evaluation was conducted on the30th day after the treatment in accordance with the standard asidentified in Table 2. The results are shown by the index numbers inTable 6.

                  TABLE 6                                                         ______________________________________                                              Dose of                                                                       active                                                                  Com-  ingre-   Phyto-                                                         pound dient    toxicity                                                                              Herbicidal effects                                     No.   (g/10 a) Or    Tr  Ec  Se  Po  Am   Ip   Xa  Cr                         ______________________________________                                        1     25       0     0   5   5   5   5    5    5   5                                6.3      0     0   4   5   5   5    4    5   4                          4     400      0     0   5   5   5   5    4    5   2                                100      0     0   3   5   5   5    2    5   1                          5     400      0     0   5   4   5   5    4    5   3                                100      0     0   4   2   5   4    3    5   2                          ______________________________________                                    

TEST EXAMPLE 5 (foliage treatment - herbicidal test)

In a pot filled with soil (surface area: 600 cm²), barnyardgrass (Ec),crabbgrass (Di), green foxtail (Se), Johnsongrass (So), smartweed (Po),slender amaranth (Am), velvetleaf (Ab), morningglory (Ip) and commoncocklebur (Xa) were sown and covered with soil in a thickness of from0.5 to 1 cm. The pot was cultured in a green house at a temperature offrom 20° to 30° C. for ten days and then, a predetermined amount of awettable powder prepared in accordance with Formulation Example 1 wasdiluted with water containing an extender, and applied to the foliage ata rate of 100 liters per 10 ares. The evaluation was conducted on the21st day after the treatment in accordance with the standard asidentified in Table 2. The results are shown by the index numbers inTable 7.

                  TABLE 7                                                         ______________________________________                                        Dose of                                                                       active                                                                        ingre-                                                                        dient       Herbicidal effects                                                (g/10 a)    Ec    Di    Se  So  Po  Am   Ab  Ip  Xa                           ______________________________________                                        Com-                                                                          pound                                                                         No.                                                                           1      6.3      5     5   5   5   5   5    5   5   5                                 1.6      5     4   5   5   5   5    4   5   5                          6      6.3      5     4   5   5   4   5    5   5   5                                 1.6      5     3   5   5   4   5    5   5   5                          10     6.3      5     3   4   5   5   5    4   5   5                                 1.6      5     2   3   5   5   5    3   4   4                          14     6.3      4     3   4   5   5   5    2   5   5                          17     6.3      5     5   5   5   5   5    5   5   5                                 1.6      5     4   5   5   5   5    3   4   5                          18     6.3      5     5   5   5   5   5    4   4   5                                 1.6      5     3   5   5   5   5    3   5   5                          19     6.3      5     5   5   5   5   5    5   5   5                                 1.6      5     5   5   5   5   5    3   4   5                          20     6.3      5     5   5   5   5   5    4   5   5                                 1.6      5     4   5   5   5   5    3   3   5                          21     6.3      5     5   5   5   5   5    4   5   5                                 1.6      5     3   5   5   5   5    3   4   5                          22     6.3      5     5   5   5   5   5    5   5   5                                 1.6      5     4   5   5   5   5    4   5   5                          23     6.3      4     3   4   4   5   5    5   5   5                          24     6.3      5     2   4   5   5   5    3   3   5                          Com-                                                                          parative                                                                      Com-                                                                          pound                                                                         No.                                                                           1      6.3      0     0   0   0   0   3    1   0   0                                 1.6      0     0   0   0   0   2    0   0   0                          2      6.3      0     0   0   0   1   2    0   0   0                                 1.6      0     0   0   0   0   1    0   0   0                          3      6.3      0     0   0   0   2   4    1   0   0                                 1.6      0     0   0   0   0   2    0   0   0                          4      6.3      0     0   0   0   0   2    0   0   0                                 1.6      0     0   0   0   0   0    0   0   0                          5      6.3      0     0   0   0   4   4    2   2   2                                 1.6      0     0   0   0   3   2    1   1   1                          ______________________________________                                    

Comparative compounds 1, 2, 3, 4 and 5 (U.S. Pat. No. 4,248,619) will beidentified below (the same applies in subsequent Tables):

Comparative Compound 1:

1,3-bis(4,6-dimethyl-2-pyrimidinyloxy)benzene

Comparative Compound 2:

1,3-bis(5-chloro-2-pyrimidinyloxy)-2-methylbenzene

Comparative Compound 3:

1,3-bis(5-chloro-2-pyrimidinyloxy)-2-nitrobenzene

Comparative Compound 4:

5-chloro-2-[3-(4,6-dimethyl-2-pyrimidinyloxy)phenoxy]pyrimidine

Comparative Compound 5:

1,2-bis(5-chloro-2-pyrimidinyloxy)benzene

TEST EXAMPLE 6 (foliage treatment - phytotoxicity test to rice)

In a pot filled with soil (surface area: 100 cm²), seeds of rice(variety: Labelle) were sown and covered with soil in a thickness of 0.5cm. The pot was cultured in a green house at a temperature of from 20°to 30° C. until 2.5 leaf stage, and then, a predetermined amount of awettable powder prepared in accordance with Formulation Example 1 wasdiluted with water containing an extender, and applied to the foliage ata rate of 100 liters per 10 ares (dose of active ingredient: 6.3 g and1.6 g per 10 ares). The phytotoxicity was evaluated on the 30th dayafter the treatment in accordance with the standard as identified inTable 2. As the results, no phytotoxicity was observed at either dose inthe case of Compound Nos. 1, 10, 17, 18, 19, 20, 21 and 22 of thepresent invention.

TEST EXAMPLE 7 (soil treatment - herbicidal test)

In a pot filled with soil (surface area: 600 cm²), seeds ofbarnyardgrass (Ec), greenfoxtail (Se), Johnsongrass (So) and waterfoxtail (Al) were sown and covered with soil in a thickness of from 0.5to 1 cm. One day later from the seeding, a predetermined amount of awettable powder prepared in accordance with Formulation Example 1 wasdiluted with water and applied to the soil surface at a rate of 100liters per 10 ares. After the application, the pot was kept in a greenhouse at a temperature of from 20° to 30° C. The evaluation wasconducted on the 20th day after the treatment in accordance with thestandard as identified in Table 2. The results are shown by the indexnumbers in Table 8.

                  TABLE 8                                                         ______________________________________                                                  Dose of                                                                       active                                                                        ingre-                                                                        dient    Herbicidal effects                                                   (g/10 a) Ec    Se      So  Al                                       ______________________________________                                        Compound No.                                                                  1           6.3        5     5     5   5                                      6           6.3        4     5     5   5                                      17          6.3        4     4     5   5                                      18          6.3        5     5     5   5                                      19          6.3        4     5     5   5                                      20          6.3        5     5     5   5                                      21          6.3        4     3     5   5                                      22          6.3        5     5     5   5                                      23          6.3        3     4     5   5                                      24          6.3        4     4     5   5                                      Comparative                                                                   Compound No.                                                                  1           6.3        0     0     0   0                                      2           6.3        0     0     1   0                                      3           6.3        0     0     0   0                                      4           6.3        0     0     0   0                                      5           6.3        0     0     1   0                                      ______________________________________                                    

TEST EXAMPLE 8 (herbicidal test against purple nutsedge as perennialweed)

In a pot filled with soil (surface area: 100 cm²), tubers of purplenutsedge (Cr) were planted and covered with soil in a thickness of 1 cm.The pot was cultured in a green house at a temperature of from 20° to30° C. until four leaf stage, and then, a predetermined amount of awettable powder prepared in accordance with Formulation Example 1 wasdiluted with water containing an extender, and applied to the foliage.The evaluation was conducted on the 20th day after the treatment inaccordance with the standard as identified in Table 2. The results areshown by the index numbers in Table 9.

                  TABLE 9                                                         ______________________________________                                                      Dose of                                                                       active                                                                        ingre- Herbicidal                                                             dient  effects                                                                (g/10 a)                                                                             Cr                                                       ______________________________________                                        Compound No.                                                                  1               25       5                                                                    6.3      4                                                    6               25       4                                                                    6.3      4                                                    7               25       4                                                                    6.3      3                                                    10              25       4                                                                    6.3      3                                                    11              25       4                                                                    6.3      3                                                    12              25       5                                                                    6.3      4                                                    14              25       4                                                                    6.3      4                                                    17              25       5                                                                    6.3      4                                                    18              25       5                                                                    6.3      4                                                    19              25       5                                                                    6.3      5                                                    20              25       5                                                                    6.3      4                                                    21              25       5                                                                    6.3      4                                                    22              25       5                                                                    6.3      5                                                    23              25       4                                                                    6.3      4                                                    Comparative                                                                   Compound No.                                                                  1               25       0                                                                    6.3      0                                                    2               25       0                                                                    6.3      0                                                    3               25       0                                                                    6.3      0                                                    4               25       0                                                                    6.3      0                                                    5               25       0                                                                    6.3      0                                                    ______________________________________                                    

We claim:
 1. A pyrimidine derivative having the formula: ##STR20##wherein R is a hydrogen atom, --CH₂ CH₂ S(O)_(n) R₁ (wherein R₁ is alower alkyl group, and n is an integer of from 0 to 2) or ##STR21##(wherein each R₁ is a lower alkyl group), A is a chlorine atom or amethoxy group, and each of D and E which may be the same or different,is a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxygroup or a halogen-substituted lower alkoxy group, or a salt thereof. 2.The pyrimidine derivative according to claim 1, wherein each of D and Ewhich may be the same or different is a hydrogen atom, a methoxy groupor an ethoxy group, or a salt thereof.
 3. The pyrimidine derivativeaccording to claim 1, wherein each of D and E which may be the same ordifferent is a hydrogen atom or a methoxy group, or a salt thereof. 4.The pyrimidine derivative according to claim 1, wherein A is a methoxygroup, and each of D and E is a methoxy group, or a salt thereof.
 5. Thepyrimidine derivative according to any one of claims 1 to 4, wherein Ris a hydrogen atom, or a salt thereof.
 6. The pyrimidine derivativeaccording to any one of claims 1 to 4, wherein R is --C₂ H₄ SCH₃, --C₂H₄ SC₂ H₅, --C₂ H₄ SOC₂ H₅ or --C₂ H₄ SO₂ C₂ H₅, or a salt thereof. 7.The pyrimidine derivative according to any one of claims 1 to 4, whereinthe salt is an alkali metal salt, an alkaline earth metal salt, atransition metal salt or an organic ammonium salt.
 8. The pyrimidinederivative according to any one of claims 1 to 4, wherein the salt is atriethanolamine salt, an ammonium salt, a sodium salt, a potassium saltor a calcium salt.
 9. The pyrimidine derivative according to claim 1,which is 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoic acid,isopropylammonium 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate,sodium 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate, tris(2hydroxyethyl)ammonium 2,6-bis[(4,6-dimethoxypyrimidin-2 yl)oxy]benzoate,bis(2-hydroxyethyl)ammonium 2,6-bis[(4,6dimethoxypyrimidin-2-yl)oxy]benzoate, calciumbis{2,6-bis[(4,6-dimethoxypyrimidin 2-yl)oxy]benzoate}, or ammonium2,6-bis[4,6-dimethoxylpyrimidin-2-yl)oxy]benzoate.
 10. A herbicidalcomposition comprising a herbicidally effective amount of a pyrimidinederivative of the formula I or its salt as defined in claim 1 and anagricultural adjuvant.
 11. A method for killing weeds which comprisesapplying a herbicidally effective amount of a pyrimidine derivative ofthe formula I or its salt as defined in claim 1 to a locus to beprotected.